Role of lattice distortion on diffuse phase transition temperatures in Bi0.5Na0.5TiO3-BaTiO3 [BNBTO] solid solutions.

Effect of lattice distortion on diffuse phase transition in BNBTO solid solutions near Morphotropic phase boundary (MPB) has been investigated. Solid solutions of (Bi_0.5Na_0.5)_1−xBa_xTiO₃ (with mole % of x= 0.04, 0.05, 0.06, 0.07 and 0.08) were prepared by the planetary ball mill method in ethanol medium. Rietveld refinement technique with rhombohedral (<italic>R3c</italic>) and tetragonal (<italic>P4bm</italic>) crystal symmetry has been employed for structural as well as phase analysis of the solid solutions. Both rhombohedral and tetragonal lattice distortion (c/a) tends toward the pseudo-cubic crystal symmetry with the increase of mole fraction of Ba²⁺ near MPB (x= 6 mole %). Also, the average crystallite size and grain size decrease with increase of mole fraction of Ba²⁺ in BNT ceramic are due to larger ionic radius of Ba²⁺ and grain boundary pinning process in the solid solutions respectively. Additionally, depolarization temperature (<italic>T</italic>_{<italic>d</italic>}) and maximum temperature (<italic>T</italic>_{<italic>m</italic>}) reduces due to the lattice distortion of both the phases in BNBTO solid solutions, which is explained extensively. Significant increase of dielectric constant has been observed near MPB composition (x=6%) in BNBTO solid solutions. [ABSTRACT FROM AUTHOR]